Ceramic materials known for use in the field of dentistry provide high strength restorations such as crowns, bridges, and the like. Some ceramic materials have flexural strength values exceeding 800 MPa when fully sintered, resulting in restorations that are resistant to chipping, breakage and wear. Material advances provide enhanced aesthetics in color and translucency while maintaining acceptable strength, and restorations may be manufactured from these materials in a cost effective manner.
Dental restorations created by computer assisted design processes may be milled by CAM processes from porous ceramic materials in the green or bisque ceramic stage, using an enlargement factor to accommodate reduction in overall size upon heating to full density. After milling, the porous restoration design is sintered to full density to produce a final restoration. Disadvantageously, the separate steps of milling the porous ceramic dental design and sintering the milled shape to form the final dental restoration, may preclude dentists from making chair-side ceramic restorations, increasing the amount of time a patient must wait for repair.
To reduce the amount of material waste to make a restoration, US2006/0204932 discloses an assemblage or library of “smart” mill blanks pre-configured into geometries and sizes that closely resemble the final dental parts. Material waste may be reduced compared to traditional mill blanks that have a single size and shape, which is desirable when using precious or semi-precious materials. The smart mill blank library is described as comprising a series of blanks with geometries that differ other than by scale, and preferably having at most, one symmetric plane. The blank is mounted in a shaping apparatus by a milling holder that has an orientation-specific attachment key for the milling machine.
Methods of making ceramic restorations from near net shape millable blanks are also known, for example, from commonly owned U.S. Patent Pub. No. 2013/0316305, which is hereby incorporated by reference in its entirety. In this document, a kit is disclosed containing millable blanks of various shapes, each shape designed to closely replicate a restoration shape thus minimizing material removal in chair-side processes. The kit comprises a variety of shapes and shades of restoration blanks, as well as chair-side software, and a chair-side milling machine to convert millable blanks into finished, contoured restorations by a dentist.